1. Field of the Invention:
This invention relates to an electronic component of rotary type.
2. Description of the Prior Art:
The following description will be given for a rotary variable resistor which forms one example of a conventional electronic component of rotary type. The conventional rotary variable resistor (potentiometer) is comprised of an operation shaft journaled in a bearing sheath provided with a threaded portion at the front end. A constant diameter central portion of an operation shaft is journaled in the bearing sheath so that the front tip of the operation shaft does not shake when the shaft is rotated. A brush holder (rotational body) is fixed at the rear tip of the operation shaft.
In actual use, the rotary variable resistor is mounted at a hole in a chassis and is fixed in place by a nut at the threaded part of the bearing sheath. The front tip of the operation shaft projects out of the hole beyond the front panel containing the hole. The diameter in the hole of the (front) panel is larger than that of the operation shaft. Therefore, even where the operation shaft axis does not lie at a correct place, i.e. at the center on the hole of the (front) panel at the mounting of the rotary variable resistor, the operation shaft does not abut the rim of the hole. Any space between the outside face of the shaft and the rim of the hole is covered by a knob, the external diameter thereof having been hitherto much larger than that of the operation shaft.
Recently, small-sized audio appliance sets such as car stereos have become popular. In such small-sized audio appliance sets with a number of rotary variable resistors disposed and lined up in front of a small-sized front panel, it is necessary to reduce the external diameter of knobs used for the rotary variable resistors and to reduce the sizes of the rotary variable resistor per se. In this situation, it becomes difficult to cover spaces around the hole of the front panel by use of the external portion of the knobs. In order to overcome this difficulty, it may be necessary to reduce the size of the spaces at the hole in the (front) panel around the shaft down to nearly zero. But, this causes problems in that the operation shaft becomes liable to abut on the internal rim of the hole at the (front) panel thereby increasing rotational torque due to friction between the shaft and the rim of the hole during rotational operation thereby generating irregular rotation of the operation shaft. In particular, when an operation shaft is moved back and forth in order to switch on and off a push switch means mounted on a rotary variable resistor, the abovementioned abutment of the operation shaft brings about fatal operational difficulties.